Field of the Invention
The present invention relates to shock absorbers.
Description of the Related Art
Many types of suspensions and supports include a spring and a damping device to help isolate that supported from the support structure or surface. For example, automotive vehicles commonly use separate springs and simple shock absorbers to support the vehicle frame on the axle assemblies. Simple shock absorbers are typically oil-filled cylinders within which a vented piston is mounted. The piston is connected is connected to a shaft which extends out of one end of the cylinder. The outer end of the shaft is mounted to one point on the vehicle and the other end of the cylinder is mounted to another point on the vehicle in parallel with the suspension spring. Thus, simple shock absorbers only provide damping and not support.
Another type of shock absorber, which is the type commonly used with motorcycles, off-road vehicles, competition automotive vehicles and off-road bicycles, combines both the suspension function and the shock absorbing function in one unit. This second type of shock absorber commonly uses a spring unit to provide the suspension function and is coupled with a damping unit to provide the damping function.
Typical shock absorbers (also referred to as shocks) provide two kinds of damping: compression damping (“CD”), and rebound damping (“RD”). One refers to a damping force created during an “inward” travel of the shaft (shortening of the shock), the other refers to damping force created during an “outward” travel of the shaft (lengthening of the shock). Generally, but not always—depending on the linkage connecting the shock to the vehicle, RD applies during outward motion and CD applies during inward motion. Some shocks are externally adjustable by the user to provide for RD and/or CD adjustment.
Piston-type shock absorbers can be designed to provide the same amount of damping during both the compression stroke and the rebound stroke. Alternatively, the fluid passageways through the vented, damping piston can be designed so that the restriction to fluid flow through the damping piston during the compression stroke is different than the restriction to fluid flow during the rebound stroke. In this case, the damping during the entire compression stroke is different than the damping during the entire rebound stroke.
Further, in a typical fluid operated damper, the damping fluid flow is inhibited by forcing fluid through a restrictive area or orifice, which effectively slows the movement of the damper during compression and rebound strokes.
During some instances of operation, conventional shock absorbers, and therefore the vehicle rider, experience cavitation, during which the shaft of the shock absorber moves into the damping fluid chamber at its full travel length without providing any damping function. What is needed is a simple solution for reducing cavitation in a shock absorber.
The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted.